EXHIBIT 5.1



                                 October 4, 2002




IDT Corporation
520 Broad Street
Newark, New Jersey 07102

         Re: IDT Corporation--Registration Statement on Form S-8
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Ladies and Gentlemen:

         I am the Secretary and General Counsel of IDT Corporation (the
"Company"), and as such I have been asked to render the following opinion in
connection with the registration statement on Form S-8 (the "Registration
Statement") to be filed with the Securities and Exchange Commission in
connection with the registration under the Securities Act of 1933, as amended,
of an aggregate of 3,000,000 shares of the Company's Class B common stock, par
value $.01 per share (the "Class B Common Stock"), which are issuable under the
Company's 1996 Stock Option and Incentive Plan, as Amended and Restated (the
"Plan").

         As your counsel in connection with the Registration Statement, I have
examined the proceedings taken by you in connection with the adoption of the
Plan and the authorization of the issuance of the Class B Common Stock under the
Plan and such other documents as I have deemed necessary to render this opinion.

         Based upon the foregoing, it is my opinion that the shares of Class B
Common Stock to be offered pursuant to the Registration Statement, when issued
and sold pursuant to the terms of the Plan or Option Agreements, as applicable,
will be validly issued, fully paid and nonassessable shares.

         I hereby consent to the filing of this Opinion as an exhibit to the
Registration Statement.

                                        Very truly yours,


                                        /s/ Joyce J. Mason
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                                        Joyce J. Mason
                                        Secretary and General Counsel